Conventionally, repairing of open circuit defects in the fine lines of high density circuitry, such as thin film conductor lines, is accomplished by closing or bridging the open defect with conductive material. Two main techniques generally used are laser chemical vapor deposition (LCVD) and wire bonding. Laser chemical vapor deposition involves bridging the open defect in the line by depositing conductive material, such as gold, across the open defect. The conductive material is typically deposited from an organometallic gas precursor. Major disadvantages associated with using LCVD for open defects repair include difficulty in controlling the dimensions, particularly, the height, of the conductive material being deposited, poor adhesion of the conductive material, and inadequate deposition control which results in depositing of conductive material in unwanted areas of the circuit being repaired.
As described in commonly assigned U.S. Pat. No. 5,079,070, issued Jan. 7, 1992, to Chalco et al., and shown in FIG. 1, FIGS. 2A-B and FIGS. 3A-B each labelled as "Prior Art", open defects repair using wire bonding generally involves a bonding tip 10 and a support sheet 20 onto which one or more repair lines 15 has been etched. The bonding tip 10 has an internal cylindrical cavity 12 which ends in a conical shape at its frontal surface 14; and the diameter of the cylindrical cavity 12 tapers down to a cylindrical opening 17 in the frontal surface 14.
The support sheet 20 is fabricated by blanket metallizing or laminating of a metal layer onto a support material. The metal layer and support material are circuitized by photoprocesses and etching procedures for forming the repair lines 15. The metal layer is then selectively etched for forming a window opening 25 therethrough for exposing the repair line 15 for performing the repair. As shown, the repair lines 15 are mechanically supported on the bottom surface 30 of the support sheet 20.
The repair process includes positioning one of the repair lines 15 over an open defect 35 of a circuit line 40. In accordance with commonly assigned U.S. Pat. No. 4,970,365, to Chalco, incorporated herein by reference, ultrasonic vibratory motion and laser energy are then utilized to enable the bonding tip 10 to bond the repair line 15 to the circuit line 40. After bonding, the support sheet 20 is lifted using a "peeling action" to detach or fracture the repair line 15 so as to complete the repair. Although the '070 patent describes this peeling action as a method to test for good repairs, it has been found that the force required for detaching the repair line 15 from the support sheet 20 may cause damage to the repair line 15, further damage to the circuit line 40 being repaired, or weakening or fracturing of the bond between the repair line 15 and the circuit line 40. This is particularly true in the case of the extremely fragile and delicate fine lines used in present day state-of-the-art high density circuitry.
Further, it has been found to be exceedingly difficult to fabricate a support sheet with repair lines having very small dimensions. For instance, it has been problematic to fabricate repair lines having a height on the order of 1-10 microns, as is oftentimes required in present day technology. In this regard, repair lines which are excessive in height may result in undesirable protrusion of the repair line above the plane of the circuit line being repaired.